A mid-turbine frame assembly is located between high and low pressure turbine rotor assemblies to support bearings and to transfer loads radially outwardly to a core casing. A mid-turbine frame supports an annular inter-turbine duct therein. The inter-turbine duct is defined between outer and inner duct walls which are interconnected by a plurality of radial hollow struts, thereby forming an annular hot gas path. The inter-turbine duct and the hollow struts are subjected to high temperatures and therefore cooling air is introduced around the inter-turbine duct and into the hollow struts to cool the same. In conventional cooling air systems for mid-turbine frames, cooling air is discharged into the hot gas path and cannot be recovered. This conventional cooling air system may not provide a sufficient pressure margin in the cooling air around the inter-turbine duct and inside of the hollow struts. Therefore, hot gas ingestion may occur.
Accordingly, there is a need to provide an improved cooling air system for a mid-turbine frame of a gas turbine engine.